Lightweight concrete compositions

ABSTRACT

A lightweight concrete composition containing from 10 to 90 volume percent of a cement composition, from 10 to 90 volume percent of particles having an average particle diameter of from 0.2 mm to 8 mm, a bulk density of from 0.03 g/cc to 0.64 g/cc, an aspect ratio of from 1 to 3, and from 0 to 50 volume percent of aggregate; where the sum of components used does not exceed 100 volume percent, and where after the lightweight concrete composition is set it has a compressive strength of at least 1700 psi as tested according to ASTM C39 after seven days. The concrete composition can be used to make concrete masonry units, construction panels, road beds and other articles.

REFERENCE TO RELATED APPLICATION

This application is a reissue of U.S. Pat. No. 7,699,929 arising fromU.S. patent application Ser. No. 12/190,724, filed Aug. 13, 2008entitled “Lightweight Concrete Compositions”, which was a continuationof Ser. No. 11/387,198 filed Mar. 22, 2006, U.S. Pat. No. 7,644,548arising from U.S. application Ser. No. 11/361,654 filed Feb. 24, 2006and entitled “Lightweight Concrete Compositions,” which claims thebenefit of priority of U.S. Provisional Application Ser. Nos. 60/664,230filed Mar. 22, 2005 entitled “Light Weight Concrete Composite Using EPSBeads” and 60/686,858 filed Jun. 2, 2005 entitled “LightweightCompositions and Materials,” which are both all herein incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to novel compositions, materials,methods of their use and methods of their manufacture that are generallyuseful as agents in the construction and building trades. Morespecifically, the compounds of the present invention can be used inconstruction and building applications that benefit from a relativelylightweight, extendable, moldable, pourable, material that has highstrength and often improved insulation properties.

2. Description of the Prior Art

In the field of preparation and use of lightweight cementitiousmaterials, such as so-called lightweight concrete, the materials thathave been available to the trades up until now have generally requiredthe addition of various constituents to achieve a strong but lightweightconcrete mass that has a high homogeneity of constituents and which isuniformly bonded throughout the mass.

U.S. Pat. Nos. 3,214,393, 3,257,338 and 3,272,765 disclose concretemixtures that contain cement, a primary aggregate, particulate expandedstyrene polymer, and a homogenizing and/or a surface-active additive.

U.S. Pat. No. 3,021,291 discloses a method of making cellular concreteby incorporating into the concrete mixture, prior to casting themixture, a polymeric material that will expand under the influence ofheat during curing. The shape and size of the polymeric particles is notcritical.

U.S. Pat. No. 5,580,378 discloses a lightweight cementitious productmade up of an aqueous cementitious mixture that can include fly ash,Portland cement, sand, lime and, as a weight saving component,micronized polystyrene particles having particle sizes in the range of50 to 2000 μm and a density of about 1 lb/ft³. The mixture can be pouredinto molded products such as foundation walls, roof tiles, bricks andthe like. The product can also be used as a mason's mortar, a plaster, astucco or a texture.

JP 9 071 449 discloses a lightweight concrete that includes Portlandcement and a lightweight aggregate such as foamed polystyrene, perliteor vermiculite as a part or all parts of the aggregate. The foamedpolystyrene has a granule diameter of 0.1-10 mm and a specific gravityof 0.01-0.08.

U.S. Pat. Nos. 5,580,378, 5,622,556, and 5,725,652 disclose lightweightcementitious products made up of an aqueous cementitious mixture thatincludes cement and expanded shale, clay, slate, fly ash, and/or lime,and a weight saving component, which is micronized polystyrene particleshaving particle sizes in the range of 50 to 2000 μm, and characterizedby having water contents in the range of from about 0.5% to 50% v/v.

U.S. Pat. No. 4,265,964 discloses lightweight compositions forstructural units such as wallboard panels and the like, which containlow density expandable thermoplastic granules; a cementitious basematerial, such as, gypsum; a surfactant; an additive which acts as afrothing agent to incorporate an appropriate amount of air into themixture; a film forming component; and a starch. The expandablethermoplastic granules are expanded as fully as possible.

WO 98 02 397 discloses lightweight-concrete roofing tiles made bymolding a hydraulic binder composition containing synthetic resin foamsas the aggregate and having a specific gravity of about 1.6 to 2.

WO 00/61519 discloses a lightweight concrete that includes a blend offrom around 40% to 99% of organic polymeric material and from 1% toaround 60% of an air entraining agent. The blend is used for preparinglightweight concrete that uses polystyrene aggregate. The blend isrequired to disperse the polystyrene aggregate and to improve the bondbetween the polystyrene aggregate and surrounding cementitious binder.

WO 01/66485 discloses a lightweight cementitious mixture containing byvolume: 5 to 80% cement, 10 to 65% expanded polystyrene particles; 10 to90% expanded mineral particles; and water sufficient to make a pastewith a substantially even distribution of expanded polystyrene afterproper mixing.

U.S. Pat. No. 6,851,235 discloses a building block that includes amixture of water, cement, and expanded polystyrene (EPS) foam beads thathave a diameter from 3.18 mm (⅛ inch) to 9.53 mm (⅜ inch) in theproportions of from 68 to 95 liters (18 to 25 gallons) water; from 150to 190 kg (325 to 425 lb) cement; and from 850 to 1400 liters (30 to 50cubic feet) Prepuff beads.

U.S. Pat. No. 5,913,791 discloses a building block that has acement-based attachment layer on one or both exterior surfaces of theblock that receives and holds a penetrating fastener such as a nail,screw, staple, or the like. One cement-based layer contains water,cement, and expanded polystyrene foam beads in first proportions and asecond exterior surface contains water, cement, and expanded polystyrenefoam beads in second proportions different than the first proportions.

Generally, the prior art recognizes the utility of using expandedpolymers, in some form, in concrete compositions, to reduce the overallweight of the compositions. The expanded polymers are primarily added totake up space and create voids in the concrete and the amount of “airspace” in the expanded polymer is typically maximized to achieve thisobjective. Generally, the prior art assumes that expanded polymerparticles will lower the strength and/or structural integrity oflightweight concrete compositions. Further, concrete articles made fromprior art lightweight concrete compositions have at best inconsistentphysical properties, such as Young's modulus, thermal conductivity, andcompressive strength, and typically demonstrate less than desirablephysical properties.

Therefore, there is a need in the art for lightweight concretecompositions that provide lightweight concrete articles havingpredictable and desirable physical properties that overcome theabove-described problems.

SUMMARY OF THE INVENTION

The present invention provides a lightweight concrete compositioncontaining from 10 to 90 volume percent of a cement composition, from 10to 90 volume percent of particles having an average particle diameter offrom 0.2 mm to 8 mm, a bulk density of from 0.028 g/cc to 0.64 g/cc, anaspect ratio of from 1 to 3, and from 0 to 50 volume percent ofaggregate where the sum of components used does not exceed 100 volumepercent; and where after the lightweight cementitious composition is setfor seven days, it has a compressive strength of at least 1700 psi astested according to ASTM C39.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scanning electron micrograph of the surface of a prepuffbead used in the invention;

FIG. 2 is a scanning electron micrograph of the interior of a prepuffbead used in the invention;

FIG. 3 is a scanning electron micrograph of the surface of a prepuffbead used in the invention;

FIG. 4 is a scanning electron micrograph of the interior of a prepuffbead used in the invention;

FIG. 5 is a scanning electron micrograph of the surface of a prepuffbead used in the invention; and

FIG. 6 is a scanning electron micrograph of the interior of a prepuffbead used in the invention.

DETAILED DESCRIPTION OF THE INVENTION

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc. used in the specification and claims are to beunderstood as modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that can vary depending upon the desired properties,which the present invention desires to obtain. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between andincluding the recited minimum value of 1 and the recited maximum valueof 10; that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. Because the disclosednumerical ranges are continuous, they include every value between theminimum and maximum values. Unless expressly indicated otherwise, thevarious numerical ranges specified in this application areapproximations.

As used herein, the term “particles containing void spaces” refer toexpanded polymer particles, prepuff particles, and other particles thatinclude cellular and/or honeycomb-type chambers at least some of whichare completely enclosed, that contain air or a specific gas orcombination of gasses, as a non-limiting example prepuff particles asdescribed herein.

As used herein the terms “cement” and “cementitious’ refer to materialsthat bond a concrete or other monolithic product, not the final productitself. In particular, hydraulic cement refers to a material that setsand hardens by undergoing a hydration reaction in the presence of asufficient quantity of water to produce a final hardened product.

As used herein, the term “cementitious mixture” refers to a compositionthat includes a cement material, and one or more fillers, adjuvants, orother aggregates and/or materials known in the art that form a slurrythat hardens upon curing. Cement materials include, but are not limitedto, hydraulic cement, gypsum, gypsum compositions, lime and the like andmay or may not include water. Adjuvants and fillers include, but are notlimited to sand, clay, fly ash, aggregate, air entrainment agents,colorants, water reducers/superplasticizers, and the like.

As used herein, the term “concrete” refers to a hard strong buildingmaterial made by mixing a cementitious mixture with sufficient water tocause the cementitious mixture to set and bind the entire mass.

As used herein, all volume and weight percentages anticipate the use ofa certain volume or weight of water. The particular amounts whenreferring to a dry-mix or ready-mix composition would be in the sameproportions anticipating that the commensurate amount of water will beadded to the dry-mix or ready-mix when it is to be finally formulated,mixed and otherwise readied for use.

All compositional ranges expressed herein are limited in total to and donot exceed 100 percent (volume percent or weight percent) in practice.Where multiple components can be present in a composition, the sum ofthe maximum amounts of each component can exceed 100 percent, with theunderstanding that, and as those skilled in the art readily understand,that the amounts of the components actually used will conform to themaximum of 100 percent.

As used herein, the terms “(meth)acrylic” and “(meth)acrylate” are meantto include both acrylic and methacrylic acid derivatives, such as thecorresponding alkyl esters often referred to as acrylates and(meth)acrylates, which the term “(meth)acrylate” is meant to encompass.

As used herein, the term “polymer” is meant to encompass, withoutlimitation, homopolymers, copolymers, graft copolymers, and blends andcombinations thereof.

In its broadest context, the present invention provides a method ofcontrolling air entrainment in a formed article. The formed article canbe made from any formable material, where particles containing voidspaces are used to entrain air in a structurally supportive manner. Anysuitable formable material can be used, so long as the particlescontaining void spaces are not damaged during the forming process.

As used herein, the term “composite material” refers to a solid materialwhich includes two or more substances having different physicalcharacteristics and in which each substance retains its identity whilecontributing desirable properties to the whole. As a non-limitingexample, composite materials can include concrete within which prepuffbeads are uniformly dispersed and embedded.

Thus, the present invention is directed to methods of controlling airentrainment where an article is formed by combining a formable materialand particles containing void spaces to provide a mixture and placingthe mixture in a form.

Although the application discloses in detail cementitious mixtures withpolymer particles, the concepts and embodiments described herein can beapplied by those skilled in the art to the other applications describedabove.

Embodiments of the present invention are directed to lightweightconcrete (LWC) compositions that includes a cementitious mixture andpolymer particles. Surprisingly, it has been found that the size,composition, structure, and physical properties of the expanded polymerparticles, and in some instances their resin bead precursors, cangreatly affect the physical properties of LWC articles made from the LWCcompositions of the invention. Of particular note is the relationshipbetween bead size and expanded polymer particle density on the physicalproperties of the resulting LWC articles.

In an embodiment of the invention, the cementitious mixture can be anaqueous cementitious mixture.

The polymer particles, which can optionally be expanded polymerparticles, are present in the LWC composition at a level of at least 10,in some instances at least 15, in other instances at least 20, inparticular situations up to 25, in some cases at least 30, and in othercases at least 35 volume percent and up to 90, in some cases up to 85,in other cases up to 78, in some instances up to 75, in other instanceup to 65, in particular instances up to 60, in some cases up to 50, andin other cases up to 40 volume percent based on the total volume of theLWC composition. The amount of polymer will vary depending on theparticular physical properties desired in a finished LWC article. Theamount of polymer particles in the LWC composition can be any value orcan range between any of the values recited above.

The polymer particles can include any particles derived from anysuitable expandable thermoplastic material. The actual polymer particlesare selected based on the particular physical properties desired in afinished LWC article. As a non-limiting example, the polymer particles,which can optionally be expanded polymer particles, can include one ormore polymers selected from homopolymers of vinyl aromatic monomers;copolymers of at least one vinyl aromatic monomer with one or more ofdivinylbenzene, conjugated dienes, alkyl methacrylates, alkyl acrylates,acrylonitrile, and/or maleic anhydride; polyolefins; polycarbonates;polyesters; polyamides; natural rubbers; synthetic rubbers; andcombinations thereof.

In an embodiment of the invention, the polymer particles includethermoplastic homopolymers or copolymers selected from homopolymersderived from vinyl aromatic monomers including styrene,isopropylstyrene, alpha-methylstyrene, nuclear methylstyrenes,chlorostyrene, tert-butylstyrene, and the like, as well as copolymersprepared by the copolymerization of at least one vinyl aromatic monomeras described above with one or more other monomers, non-limitingexamples being divinylbenzene, conjugated dienes (non-limiting examplesbeing butadiene, isoprene, 1,3- and 2,4-hexadiene), alkyl methacrylates,alkyl acrylates, acrylonitrile, and maleic anhydride, wherein the vinylaromatic monomer is present in at least 50% by weight of the copolymer.In an embodiment of the invention, styrenic polymers are used,particularly polystyrene. However, other suitable polymers can be used,such as polyolefins (e.g. polyethylene, polypropylene), polycarbonates,polyphenylene oxides, and mixtures thereof.

In a particular embodiment of the invention, the polymer particles areexpandable polystyrene (EPS) particles. These particles can be in theform of beads, granules, or other particles convenient for expansion andmolding operations.

In the present invention, particles polymerized in a suspension process,which are essentially spherical resin beads, are useful as polymerparticles or for making expanded polymer particles. However, polymersderived from solution and bulk polymerization techniques that areextruded and cut into particle sized resin bead sections can also beused.

In an embodiment of the invention, resin beads (unexpanded) containingany of the polymers or polymer compositions described herein have aparticle size of at least 0.2, in some situations at least 0.33, in somecases at least 0.35, in other cases at least 0.4, in some instances atleast 0.45 and in other instances at least 0.5 mm. Also, the resin beadscan have a particle size of up to 3, in some instances up to 2, in otherinstances up to 2.5, in some cases up to 2.25, in other cases up to 2,in some situations up to 1.5 and in other situations up to 1 mm. In thisembodiment, the physical properties of LWC articles made according tothe invention have inconsistent or undesirable physical properties whenresin beads having particle sizes outside of the above described rangesare used to make the expanded polymer particles. The resin beads used inthis embodiment can be any value or can range between any of the valuesrecited above.

The expandable thermoplastic particles or resin beads can optionally beimpregnated using any conventional method with a suitable blowing agent.As a non-limiting example, the impregnation can be achieved by addingthe blowing agent to the aqueous suspension during the polymerization ofthe polymer, or alternatively by re-suspending the polymer particles inan aqueous medium and then incorporating the blowing agent as taught inU.S. Pat. No. 2,983,692. Any gaseous material or material which willproduce gases on heating can be used as the blowing agent. Conventionalblowing agents include aliphatic hydrocarbons containing 4 to 6 carbonatoms in the molecule, such as butanes, pentanes, hexanes, and thehalogenated hydrocarbons, e.g. CFC's and HCFC'S, which boil at atemperature below the softening point of the polymer chosen. Mixtures ofthese aliphatic hydrocarbon blowing agents can also be used.

Alternatively, water can be blended with these aliphatic hydrocarbonsblowing agents or water can be used as the sole blowing agent as taughtin U.S. Pat. Nos. 6,127,439; 6,160,027; and 6,242,540 in these patents,water-retaining agents are used. The weight percentage of water for useas the blowing agent can range from 1 to 20%. The texts of U.S. Pat.Nos. 6,127,439, 6,160,027 and 6,242,540 are incorporated herein byreference.

The impregnated polymer particles or resin beads are optionally expandedto a bulk density of at least 1.75 lb/ft³ (0.028 g/cc), in somecircumstances at least 2 lb/ft³ (0.032 g/cc) in other circumstances atleast 3 lb/ft³ (0.048 g/cc) and in particular circumstances at least3.25 lb/ft³ (0.052 g/cc) or 3.5 lb/ft³ (0.056 g/cc). When non-expandedresin beads are used higher bulk density beads can be used. As such, thebulk density can be as high as 40 lb/ft³ (0.64 g/cc). In othersituations, the polymer particles are at least partially expanded andthe bulk density can be up to 35 lb/ft³ (0.56 g/cc), in some cases up to30 lb/ft³ (0.48 g/cc), in other cases up to 25 lb/ft³ (0.4 g/cc), insome instances up to 20 lb/ft³ (0.32 g/cc), in other instances up to 15lb/ft³ (0.24 g/cc) and in certain circumstances up to 10 lb/ft³ (0.16g/cc). The bulk density of the polymer particles can be any value orrange between any of the values recited above. The bulk density of thepolymer particles, resin beads and/or prepuff particles is determined byweighing a known volume of polymer particles, beads and/or prepuffparticles (aged 24 hours at ambient conditions).

The expansion step is conventionally carried out by heating theimpregnated beads via any conventional heating medium, such as steam,hot air, hot water, or radiant heat. One generally accepted method foraccomplishing the pre-expansion of impregnated thermoplastic particlesis taught in U.S. Pat. No. 3,023,175.

The impregnated polymer particles can be foamed cellular polymerparticles as taught in U.S. patent application Ser. No. 10/021,716, theteachings of which are incorporated herein by reference. The foamedcellular particles can be polystyrene that are expanded and contain avolatile blowing agent at a level of less than 14 wt %, in somesituations less than 6 wt %, in some cases ranging from about 2 wt % toabout 5 wt %, and in other cases ranging from about 2.5 wt % to about3.5 wt % based on the weight of the polymer.

An interpolymer of a polyolefin and in situ polymerized vinyl aromaticmonomers that can be included in the expanded thermoplastic resin orpolymer particles according to the invention is disclosed in U.S. Pat.Nos. 4,303,756 and 4,303,757 and U.S. Application Publication2004/0152795, the relevant portions of which are herein incorporated byreference.

The polymer particles can include customary ingredients and additives,such as flame retardants, pigments, dyes, colorants, plasticizers, moldrelease agents, stabilizers, ultraviolet light absorbers, moldprevention agents, antioxidants, rodenticides, insect repellants, and soon. Typical pigments include, without limitation, inorganic pigmentssuch as carbon black, graphite, expandable graphite, zinc oxide,titanium dioxide, and iron oxide, as well as organic pigments such asquinacridone reds and violets and copper phthalocyanine blues andgreens.

In a particular embodiment of the invention the pigment is carbon black,a non-limiting example of such a material being EPS SILVER®, availablefrom NOVA Chemicals Inc.

In another particular embodiment of the invention the pigment isgraphite, a non-limiting example of such a material being NEOPOR®,available from BASF Aktiengesellschaft Corp., Ludwigshafen am Rhein,Germany.

When materials such as carbon black and/or graphite are included in thepolymer particles, improved insulating properties, as exemplified byhigher R values for materials containing carbon black or graphite (asdetermined using ASTM-C518), are provided. As such, the R value of theexpanded polymer particles containing carbon black and/or graphite ormaterials made from such polymer particles are at least 5% higher thanobserved for particles or resulting articles that do not contain carbonblack and/or graphite.

The expanded polymer particles or prepuff particles can have an averageparticle size of at least 0.2, in some circumstances at least 0.3, inother circumstances at least 0.5, in some cases at least 0.75, in othercases at least 0.9 and in some instances at least 1 mm and can be up to8, in some circumstances up to 6, in other circumstances up to 5, insome cases up to 4, in other cases up to 3, and in some instances up to2.5 mm. When the size of the expanded polymer particles or prepuffparticles are too small or too large, the physical properties of LWCarticles made using the present LWC composition can be undesirable. Theaverage particle size of the expanded polymer particles or prepuffparticles can be any value and can range between any of the valuesrecited above. The average particle size of the expanded polymerparticles or prepuff particles can be determined using laser diffractiontechniques or by screening according to mesh size using mechanicalseparation methods well known in the art.

In an embodiment of the invention, the polymer particles or expandedpolymer particles have a minimum average cell wall thickness, whichhelps to provide desirable physical properties to LWC articles madeusing the present LWC composition. The average cell wall thickness andinner cellular dimensions can be determined using scanning electronmicroscopy techniques known in the art. The expanded polymer particlescan have an average cell wall thickness of at least 0.15 μm, in somecases at least 0.2 μm and in other cases at least 0.25 μm. Not wishingto be bound to any particular theory, it is believed that a desirableaverage cell wall thickness results when resin beads having theabove-described dimensions are expanded to the above-describeddensities.

In an embodiment of the invention, the polymer beads are optionallyexpanded to form the expanded polymer particles such that a desirablecell wall thickness as described above is achieved. Though manyvariables can impact the wall thickness, it is desirable, in thisembodiment, to limit the expansion of the polymer bead so as to achievea desired wall thickness and resulting expanded polymer particlestrength. Optimizing processing steps and blowing agents can expand thepolymer beads to a minimum of 1.75 lb/ft³ (0.028 g/cc). This property ofthe expanded polymer bulk density, can be described by pcf (lb/ft³) orby an expansion factor (cc/g).

As used herein, the term “expansion factor” refers to the volume a givenweight of expanded polymer bead occupies, typically expressed as cc/g.

In order to provide expanded polymer particles with desirable cell wallthickness and strength, the expanded polymer particles are not expandedto their maximum expansion factor; as such an extreme expansion yieldsparticles with undesirably thin cell walls and insufficient strength.Further, the polymer beads can be expanded at least 5%, in some cases atleast 10%, and in other cases at least 15% of their maximum expansionfactor. However, so as not to cause the cell wall thickness to be toothin, the polymer beads are expanded up to 80%, in some cases up to 75%,in other cases up to 70%, in some instances up to 65%, in otherinstances up to 60%, in some circumstances up to 55%, and in othercircumstances up to 50% of their maximum expansion factor. The polymerbeads can be expanded to any degree indicated above or the expansion canrange between any of the values recited above. Typically, the polymerbeads or prepuff particles do not further expand when formulated intothe present cementitious compositions and do not further expand whilethe cementitious compositions set, cure and/or harden.

As used herein, the term “prepuff” refers to an expandable particle,resin and/or bead that has been expanded, but has not been expanded toits maximum expansion factor.

The prepuff or expanded polymer particles typically have a cellularstructure or honeycomb interior portion and a generally smoothcontinuous polymeric surface as an outer surface, i.e., a substantiallycontinuous outer layer. The smooth continuous surface can be observedusing scanning electron microscope (SEM) techniques at 1000×magnification. SEM observations do not indicate the presence of holes inthe outer surface of the prepuff or expanded polymer particles, as shownin FIGS. 1,3 and 5. Cutting sections of the prepuff or expanded polymerparticles and taking SEM observations reveals the generally honeycombstructure of the interior of the prepuff or expanded polymer particles,as shown in FIGS. 2, 4 and 6.

The polymer particles or expanded polymer particles can have anycross-sectional shape that allows for providing desirable physicalproperties in LWC articles. In an embodiment of the invention, theexpanded polymer particles have a circular, oval or ellipticalcross-section shape. In embodiments of the invention, the prepuff orexpanded polymer particles have an aspect ratio of 1, in some cases atleast 1 and the aspect ratio can be up to 3, in some cases up to 2 andin other cases up to 1.5. The aspect ratio of the prepuff or expandedpolymer particles can be any value or range between any of the valuesrecited above.

The cementitious mixture is present in the LWC composition at a level ofat least 10, in some instances at least 15, in other instances at least22, in some cases at least 40 and in other cases at least 50 volumepercent and can be present at a level of up to 90, in some circumstancesup to 85, in other circumstances up to 80, in particular cases up to 75,in some cases up to 70, in other cases up to 65, and in some instancesup to 60 volume percent of the LWC composition. The cementitious mixturecan be present in the LWC composition at any level stated above and canrange between any of the levels stated above.

In an embodiment of the invention, the cementitious mixture includes ahydraulic cement composition. The hydraulic cement composition can bepresent at a level of at least 3, in certain situations at least 5, insome cases at least 7.5, and in other cases at least 9 volume percentand can be present at levels up to 40, in some cases up to 35, in othercases up to 32.5, and in some instances up to 30 volume percent of thecementitious mixture. The cementitious mixture can include the hydrauliccement composition at any of the above-stated levels or at levelsranging between any of levels stated above.

In a particular embodiment of the invention, the hydraulic cementcomposition can be one or more materials selected from Portland cements,pozzolana cements, gypsum cements, aluminous cements, magnesia cements,silica cements, and slag cements. In a particular embodiment of theinvention the cement composition is type III Portland cement.

In an embodiment of the invention, the cementitious mixture canoptionally include other aggregates and adjuvants known in the artincluding but not limited to sand, additional aggregate, plasticizersand/or fibers. Suitable fibers include, but are not limited to glassfibers, silicon carbide, aramid fibers, polyester, carbon fibers,composite fibers, fiberglass, and combinations thereof as well as fabriccontaining the above-mentioned fibers, and fabric containingcombinations of the above-mentioned fibers.

Non-limiting examples of fibers that can be used in the inventioninclude MeC-GRID® and C-GRID® available from TechFab, LLC, Anderson,S.C., KEVLAR® available from E.I. du Pont de Nemours and Company,Wilmington Del., TWARON® available from Teijin Twaron B.V., Arnheim, theNetherlands, SPECTRA® available from Honeywell International Inc.,Morristown, N.J., DACRON® available from Invista North America S.A.R.L.Corp. Willmington, Del., and VECTRAN® available from Hoechst CellaneseCorp., New York, N.Y. The fibers can be used in a mesh structure,intertwined, interwoven, and oriented in any desirable direction.

In a particular embodiment of the invention fibers can make up at least0.1, in some cases at least 0.5, in other cases at least 1, and in someinstances at least 2 volume percent of the LWC composition. Further,fibers can provide up to 10, in some cases up to 8, in other cases up to7, and in some instances up to 5 volume percent of the LWC composition.The amount of fibers is adjusted to provide desired properties to theLWC composition. The amount of fibers can be any value or range betweenany of the values recited above.

Further to this embodiment, the additional aggregate can include, but isnot limited to, one or more materials selected from common aggregatessuch as sand, stone, and gravel. Common lightweight aggregates caninclude ground granulated blast furnace slag, fly ash, glass, silica,expanded slate and clay; insulating aggregates such as pumice, perlite,vermiculite, scoria, and diatomite; LWC aggregate such as expandedshale, expanded slate, expanded clay, expanded slag, fumed silica,pelletized aggregate, extruded fly ash, tuff, and macrolite; and masonryaggregate such as expanded shale, clay, slate, expanded blast furnaceslag, sintered fly ash, coal cinders, pumice, scoria, and pelletizedaggregate.

When included, the other aggregates and adjuvants are present in thecementitious mixture at a level of at least 0.5, in some cases at least1, in other cases at least 2.5, in some instances at least 5 and inother instances at least 10 volume percent of the cementitious mixture.Also, the other aggregates and adjuvants can be present at a level of upto 95, in some cases up to 90, in other cases up to 85, in someinstances up to 65 and in other instances up to 60 volume percent of thecementitious mixture. The other aggregates and adjuvants can be presentin the cementitious mixture at any of the levels indicated above or canrange between any of the levels indicated above.

In an embodiment of the invention, all or a portion of the sand or otherfine aggregate used in the present cementitious mixture and/orlightweight concrete composition has a fineness modulus of less than 2,in some cases less than 1.9 and in other cases less than 1.8. As usedherein, “fineness modulus” or “FM” refers to an empirical factor thatgives a relative measure of the proportions of fine and coarse particlesin an aggregate. FM is a value used to indicate the relative fineness orcoarseness of a fine aggregate and can be determined according to ASTM C117. Although ASTM C 117 can be consulted for precise details, and isincorporated by reference herein in its entirety, it can be summarizedas follows. The FM is obtained by sieving a 500-gram sample of sandthrough a series of standard sieves (Nos. 4, 8, 16, 30, 50, and 100).The weight retained on each sieve is converted into a cumulativepercentage retained, starting with the No. 4 sieve. The sum of the sixpercentages are divided by 100. The resulting answer is the finenessmodulus.

In a particular embodiment of the invention sand and/or other fineaggregate can make up at least 10, in some cases at least 15, in othercases at least 20 volume percent of the LWC composition. Further, sandand/or other fine aggregate can provide up to 50, in some cases up to45, in other cases up to 40, and in some instances up to 35 volumepercent of the LWC composition. The amount of sand and/or other fineaggregate is adjusted to provide desired properties to the LWCcomposition. The amount of sand and/or other fine aggregate can be anyvalue or range between any of the values recited above.

In a particular embodiment of the invention coarse aggregate (aggregatehaving an FM value of greater than 4) can make up at least 1, in somecases at least 2, and in other cases at least 3 volume percent of theLWC composition. Further, coarse aggregate can provide up to 20, in somecases up to 15, in other cases up to 10, and in some instances up to 8volume percent of the LWC composition. The amount of coarse aggregate isadjusted to provide desired properties to the LWC composition. Theamount of coarse aggregate sand can be any value or range between any ofthe values recited above.

In embodiments of the invention, the lightweight concrete compositionscan contain one or more additives, non-limiting examples of such beinganti-foam agents, water-proofing agents, dispersing agents,set-accelerators, set-retarders, plasticizing agents, superplasticizingagents, freezing point decreasing agents, adhesiveness-improving agents,and colorants. The additives are typically present at less than onepercent by weight with respect to total weight of the composition, butcan be present at from 0.1 to 3 weight percent.

Suitable dispersing agents or plasticizers that can be used in theinvention include, but are not limited to hexametaphosphate,tripolyphosphate, polynaphthalene sulphonate, sulphonated polyamine andcombinations thereof.

Suitable plasticizing agents that can be used in the invention include,but are not limited to polyhydroxycarboxylic acids or salts thereof,polycarboxylates or salts thereof; lignosulfonates, polyethyleneglycols, and combinations thereof.

Suitable superplasticizing agents that can be used in the inventioninclude, but are not limited to alkaline or earth alkaline metal saltsof lignin sulfonates; lignosulfonates, alkaline or earth alkaline metalsalts of highly condensed naphthalene sulfonic acid/formaldehydecondensates; polynaphthalene sulfonates, alkaline or earth alkalinemetal salts of one or more polycarboxylates (such as poly(meth)acrylatesand the polycarboxylate comb copolymers described in U.S. Pat. No.6,800,129, the relevant portions of which are herein incorporated byreference); alkaline or earth alkaline metal salts ofmelamine/formaldehyde/sulfite condensates; sulfonic acid esters;carbohydrate esters; and combinations thereof.

Suitable set-accelerators that can be used in the invention include, butare not limited to soluble chloride salts (such as calcium chloride),triethanolamine, paraformaldehyde, soluble formate salts (such ascalcium formate), sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium sulfate, 12CaO.7Al₂O₃, sodium sulfate, aluminumsulfate, iron sulfate, the alkali metal nitrate/sulfonated aromatichydrocarbon aliphatic aldehyde condensates disclosed in U.S. Pat. No.4,026,723, the water soluble surfactant accelerators disclosed in U.S.Pat. No. 4,298,394, the methylol derivatives of amino acids acceleratorsdisclosed in U.S. Pat. No. 5,211,751, and the mixtures of thiocyanicacid salts, alkanolamines, and nitric acid salts disclosed in U.S. Pat.No. Re. 35,194, the relevant portions of which are herein incorporatedby reference, and combinations thereof.

Suitable set-retarders that can be used in the invention include, butare not limited to lignosulfonates, hydroxycarboxylic acids (such asgluconic acid, citric acid, tartaric acid, malic acid, salicylic acid,glucoheptonic acid, arabonic acid, acid, and inorganic or organic saltsthereof such as sodium, potassium, calcium, magnesium, ammonium andtriethanolamine salt), cardonic acid, sugars, modified sugars,phosphates, borates, silico-fluorides, calcium bromate, calcium sulfate,sodium sulfate, monosaccharides such as glucose, fructose, galactose,saccharose, xylose, apiose, ribose and invert sugar, oligosaccharidessuch as disaccharides and trisaccharides, such oligosaccharides asdextrin, polysaccharides such as dextran, and other saccharides such asmolasses containing these; sugar alcohols such as sorbitol; magnesiumsilicofluoride; phosphoric acid and salts thereof, or borate esters;aminocarboxylic acids and salts thereof; alkali-soluble proteins; humicacid; tannic acid; phenols; polyhydric alcohols such as glycerol;phosphonic acids and derivatives thereof, such asaminotri(methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonicacid, ethylenediaminetetra(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid), and alkali metal oralkaline earth metal salts thereof, and combinations of theset-retarders indicated above.

Suitable defoaming agents that can be used in the invention include, butare not limited to silicone-based defoaming agents (such asdimethylpolysiloxane, diemthylsilicone oil, silicone paste, siliconeemulsions, organic group-modified polysiloxanes (polyorganosiloxanessuch as dimethylpolysiloxane), fluorosilicone oils, etc.), alkylphosphates (such as tributyl phosphate, sodium octylphosphate, etc.),mineral oil-based defoaming agents (such as kerosene, liquid paraffin,etc.), fat- or oil-based defoaming agents (such as animal or vegetableoils, sesame oil, castor oil, alkylene oxide adducts derived therefrom,etc.), fatty acid-based defoaming agents (such as oleic acid, stearicacid, and alkylene oxide adducts derived therefrom, etc.), fatty acidester-based defoaming agents (such as glycerol monoricinolate,alkenylsuccinic acid derivatives, sorbitol monolaurate, sorbitoltrioleate, natural waxes, etc.), oxyalkylene type defoaming agents,alcohol-based defoaming agents: octyl alcohol, hexadecyl alcohol,acetylene alcohols, glycols, etc.), amide-based defoaming agents (suchas acrylate polyamines, etc.), metal salt-based defoaming agents (suchas aluminum stearate, calcium oleate, etc.) and combinations of theabove-described defoaming agents.

Suitable freezing point decreasing agents that can be used in theinvention include, but are not limited to ethyl alcohol, calciumchloride, potassium chloride, and combinations thereof.

Suitable adhesiveness-improving agents that can be used in the inventioninclude, but are not limited to polyvinyl acetate, styrene-butadiene,homopolymers and copolymers of (meth)acrylate esters, and combinationsthereof.

Suitable water-repellent or water-proofing agents that can be used inthe invention include, but are not limited to fatty acids (such asstearic acid or oleic acid), lower alkyl fatty acid esters (such asbutyl stearate), fatty acid salts (such as calcium or aluminumstearate), silicones, wax emulsions, hydrocarbon resins, bitumen, fatsand oils, silicones, paraffins, asphalt, waxes, and combinationsthereof. Although not used in many embodiments of the invention, whenused suitable air-entraining agents include, but are not limited tovinsol resins, sodium abietate, fatty acids and salts thereof, tensides,alkyl-aryl-sulfonates, phenol ethoxylates, lignosulfonates, and mixturesthereof.

The cementitious mixture, expanded polymer particles, and any otheraggregates, additives and/or adjuvants are mixed using methods wellknown in the art. In an embodiment of the invention a liquid, in someinstances water, is also mixed into the other ingredients.

In an embodiment of the invention, a dry mixture (i.e., containingminimal or no added water) can be produced, packaged and stored forfuture use. Such a dry mixture or “ready mix” can later be mixed withwater to provide the lightweight concrete compositions described herein.

In an embodiment of the invention, the concrete composition is adispersion where the cementitious mixture provides, at least in part, acontinuous phase and the polymer particles and/or expanded polymerparticles exist as a dispersed phase of discrete particles in thecontinuous phase.

As a particular and non-limiting embodiment of the invention, theconcrete composition is substantially free of wetting agents ordispersing agents used to stabilize the dispersion.

As a non-limiting embodiment of the invention and as not wishing to belimited to any single theory, some factors that can affect theperformance of the present LWC composition include the volume fractionof the expanded resin bead, the average expanded bead size and themicrostructure created by the inter-bead spacing within the concrete. Inthis embodiment, the inter-bead spacing can be estimated using atwo-dimensional model. For simplicity in description, the inter-beadspacing can be limited to the bead radius. Additionally, and withoutmeaning to limit the invention in any way, it is assumed in thisembodiment that the beads are arranged in a cubic lattice, bead sizedistribution in the LWC composition is not considered, and thedistribution of expanded bead area in the cross-section is notconsidered. In order to calculate the number of beads per sample, athree-dimensional test cylinder is assumed.

The smaller the expanded bead size, the greater the number of expandedbeads required to maintain the same expanded bead volume fraction asdescribed by equation 1 below. As the number of expanded beads increasesexponentially, the spacing between the expanded beads decreases.N_(b)=K/B³  (1)N_(b) represents the number of expanded beads.

A LWC test specimen with diameter D and height H (usually 2″×4″ or6″×12″), containing dispersed expanded polymer beads of average expandedbead diameter B, and a given volume fraction V_(d) contains an amount ofexpanded polymer beads N_(b) given by equation 1:

Note that N_(b) is inversely proportional to the cube of the expandedpolymer bead diameter. The constant of proportionality, K=1.5 V_(d)HD²,is a number that is dependent only on the sample size and the volumefraction of expanded polymer beads. Thus for a given sample size, andknown expanded polymer bead volume fraction, the number of beadsincreases to a third power as the bead diameter decreases.

As a non-limiting example, for a 2″×4″ LWC specimen, at 90 pcf (lb/ft³)(corresponding to expanded polymer bead 43% volume fraction withpre-puff bulk density of 1.25 pcf), the number of beads increasesfourfold and sevenfold moving from a 0.65 mm bead to 0.4 mm and 0.33 mmbeads respectively. At 2.08 pcf, the increase in the number of beads issixfold and sevenfold for 0.4 mm and 0.33 mm beads respectively. At 5pcf, the increases are twofold and threefold respectively. Thus, thedensity correlates to the bead size. As shown below, the density alsoaffects the cell wall thickness. The strength of a concrete matrixpopulated by expanded beads is typically affected by the cell wallstiffness and thickness.

In an embodiment of the invention, where monodisperse spherical cellsare assumed, it can be shown that the mean cell diameter d is related tothe mean wall thickness 6 by equation 2:

$\begin{matrix}{d = {\delta/\left( {\frac{1}{\sqrt{1 - {\rho/\rho_{s}}}} - 1} \right)}} & (2)\end{matrix}$where ρis the density of the foam and ρ_(s), is the density of the solidpolymer bead.

Thus for a given polymer, depending on the particular expansion processused, one can obtain the same cell wall thickness (at a given cell size)or the same cell size at various values of δ. The density is controllednot only by the cell size but also by varying the thickness of the cellwall.

The table below exemplifies the variation of expanded polymer beaddensity with bead size for three classes of beads.

Foam Particle Expansion Average Number of Bead Size, Density Size factorbeads for 43% volume microns (pcf) (mm) (cc/g) fraction 650 2.00 1.76431 96,768 650 3.00 1.541 21 145,152 650 4.00 1.400 16 193,536 400 2.001.086 31 415,233 400 3.00 0.949 21 622,849 400 4.00 0.862 16 830,466 3302.00 0.896 31 739,486 330 3.00 0.783 21 1,109,229 330 4.00 0.711 161,478,972

Desirable microstructures and/or morphologies can fall into distinctclasses. The first is a bicontinous or co-continuous composite withspecial interfaces and the second includes special inclusions in aconnected matrix. The effective properties of both bicontinous andsingly connected microstructures are described by known optimalcross-property bounds.

In many cases, the smaller the beads, the greater the number of beadsrequired to maintain the same expanded polymer bead volume fraction asdescribed by equation 1. As the number of beads increases exponentially,the spacing between the beads decreases.

The optimal bounds can be described by a number of relationsrepresenting critical numbers or limits. As a non-limiting example, fora given volume fraction, there is often a critical bead sizecorresponding to a critical number of beads that can be dispersed toprovide a desired morphology such that all the beads are isolated andthe concrete is singly connected. It is also possible to form amorphology where all of the beads are non-isolated but contacting.

Finite element analysis of a 2-dimensional cross section was performedusing ANSYS® (a finite element analysis program available from ANSYSInc., Canonsburg, Pa.). In the finite element mesh of the cross-section,the beads are modeled as non-contacting or isolated circles in a singlyconnected concrete matrix.

The results demonstrate that under loading, the stresses build up in adirection perpendicular to the load axis. The maximum stressconcentrations are at the horizontal boundary between the expandedpolymer beads, which tend to be deformed from a circular shape to anelliptical shape.

In a particular embodiment of the invention, the concrete compositioncontains at least some of the expanded polymer particles or prepuffparticles arranged in a cubic or hexagonal lattice.

In an embodiment of the invention, the present LWC composition issubstantially free of air entraining agents, which are typically addedto create air cells or voids in a batch of concrete.

In another embodiment of the invention, the LWC composition can includereinforcement fibers. Such fibers act as reinforcing components, havinga large aspect ratio, that is, their length/diameter ratio is high, sothat a load is transferred across potential points of fracture.Non-limiting examples of suitable fibers include fiberglass strands ofapproximately one to one and three fourths inches in length, althoughany material can be used that has a higher Young's modulus than thematrix of the cementitious mixture, polypropylene fiber and other fibersas described above.

The LWC compositions according to the invention can be set and/orhardened to form final concrete articles using methods well known in theart.

The density of the set and/or hardened final concrete articlescontaining the LWC composition of the invention can be at least 40lb/ft³ (0.64 g/cc), in some cases at least 45 lb/ft³ (0.72 g/cc) and inother cases at least 50 lb/ft³ (0.8 g/cc) lb/ft³ and the density can beup to 130 lb/ft³ (2.1 g/cc), in some cases 120 lb/ft³ (1.9 g/cc), inother cases up to 115 lb/ft³ (1.8 g/cc), in some circumstances up to 110lb/ft³ (1.75 g/cc), in other circumstances up to 105 lb/ft³ (1.7 g/cc),in some instances up to 100 lb/ft³ (1.6 g/cc), and in other instances upto 95 lb/ft³ (1.5 g/cc). The density of the present concrete articlescan be any value and can range between any of the values recited above.The density of the LWC composition is determined according to ASTM C138.

In a particular embodiment of the invention, the LWC compositioncontains containing from 10 to 60 volume percent of a cement compositionthat includes type III Portland Cement; from 20 to 78 volume percent ofexpanded polymer particles having an average particle diameter of from0.2 mm to 5 mm, a bulk density of from 0.032 g/cc to 0.56 g/cc, and anaspect ratio of from 1 to 2; from 5 to 35 volume percent of one or moreaggregates; and from 0.1 to 1 volume percent of one or more additivesselected from anti-foam agents, water-proofing agents, dispersingagents, set-accelerators, set-retarders, plasticizing agents,superplasticizing agents, freezing point decreasing agents,adhesiveness-improving agents, colorants and combinations thereof; wherethe sum of components used does not exceed 100 volume percent and whereafter the lightweight cementitious composition is set, it has acompressive strength of at least 2000 psi as tested according to ASTMC39 after seven days.

The LWC compositions can be used in most, if not all, applications wheretraditional concrete formulations are used. As non-limiting examples,the present LWC compositions can be used in structural and architecturalapplications, non-limiting examples being party walls, ICF or SIPstructures, bird baths, benches, shingles, siding, drywall, cementboard, decorative pillars or archways for buildings, etc., furniture orhousehold applications such as counter tops, in-floor radiant heatingsystems, floors (primary and secondary), tilt-up walls, sandwich wallpanels, as a stucco coating, road and airport safety applications suchas arresting walls, Jersey Barriers, sound barriers and walls, retainingwalls, runway arresting systems, air entrained concrete, runaway truckramps, flowable excavatable backfill, and road construction applicationssuch as road bed material and bridge deck material.

Additionally, LWC articles according to the invention readily acceptdirect attachment of screws, as a non-limiting example drywall screwsand nails, which can be attached by traditional, pneumatic, or powderactuated devices. This allows easy attachment of materials such asplywood, drywall, studs and other materials commonly used in theconstruction industry, which cannot be done using traditional concreteformulations.

When the LWC compositions of the invention are used in road bedconstruction, the polymer particles can aid in preventing and orminimizing crack propagation, especially when water freeze-thaw isinvolved.

In an embodiment of the invention, the set and/or hardened LWCcompositions according to the invention are used in structuralapplications and can have a minimum compressive strength for loadbearing masonry structural applications of at least 1700 psi (119.5kgf/cm²), in other cases at least 1800 psi (126.5 kgf/cm²), in someinstances at least 1900 psi, and in other instances at least 2000 psi(140.6 kgf/cm²). For structural lightweight concrete the compositionscan have a minimum compressive strength of at least 2500 psi (175.8kgf/cm²). Compressive strengths are determined according to ASTM C39 atseven days.

Although ASTM C39 can be consulted for precise details, and isincorporated by reference herein in its entirety, it can be summarizedas providing a test method that consists of applying a compressive axialload to molded cylinders or cores at a rate which is within a prescribedrange until failure occurs. The testing machine is equipped with twosteel bearing blocks with hardened faces, one which is a sphericallyseated block that will bear on the upper surface of the specimen, andthe other a solid block on which the specimen rests. The load is appliedat a rate of movement (platen to crosshead measurement) corresponding toa stress rate on the specimen of 35±7 psi/s (0.25±0.05 Mpa/s). Thecompressive load is applied until the load indicator shows that the loadis decreasing steadily and the specimen displays a well-defined fracturepattern. The compressive strength is calculated by dividing the maximumload carried by the specimen during the test by the cross-sectional areaof the specimen.

The compositions of the invention are well suited to the fabrication ofmolded construction articles and materials, non-limiting examples ofsuch include wall panels including tilt-up wall panels, T beams, doubleT beams, roofing tiles, roof panels, ceiling panels, floor panels, Ibeams, foundation walls and the like. The compositions exhibit greaterstrength than prior art LWC compositions.

In an embodiment of the invention, the molded construction articles andmaterials can be pre-cast and/or pre-stressed.

As used herein, “pre-cast” concrete refers to concrete poured into amold or cast of a required shape and allowed to cure and/or hardenbefore being taken out and put into a desired position.

As used herein, “pre-stressed” concrete refers to concrete whose tensionhas been improved by using prestressing tendons (in many cases hightensile steel cable or rods), which are used to provide a clamping loadproducing a compressive strength that offsets the tensile stress thatthe concrete member would otherwise experience due to a bending load.Any suitable method known in the art can be used to pre-stress concrete.Suitable methods include, but are not limited to Pre-tensioned concrete,where concrete is cast around already tensioned tendons, andpost-tensioned concrete, where compression is applied after the pouringand curing processes.

A particular advantage that the present invention provides is that theset concrete composition and/or molded construction articles formed fromsuch compositions can be readily cut and/or sectioned using conventionalmethods as opposed to having to use specialized concrete or diamondtipped cutting blades and/or saws. This provides substantial time andcost savings when customizing concrete articles.

The compositions can be readily cast into molds according to methodswell known to those of skill in the art for, as non-limiting examples,roofing tiles, paver, or other articles in virtually any threedimensional configuration desired, including configurations havingcertain topical textures such as having the appearance of wooden shakes,slate shingles or smooth faced ceramic tiles. A typical shingle can haveapproximate dimensions of ten inches in width by seventeen inches inlength by one and three quarters inches in thickness. In the molding ofroofing materials, the addition of an air entrainment agent makes thefinal product more weatherproof in terms of resistance to freeze/thawdegradation.

When foundation walls are poured using the LWC compositions of theinvention, the walls can be taken above grade due to the lighter weight.Ordinarily, the lower part of the foundation wall has a tendency to blowoutwards under the sheer weight of the concrete mixture, but the lighterweight of the compositions of the invention tend to lessen the chancesof this happening. Foundation walls prepared using the present LWCcompositions can readily take conventional fasteners used inconventional foundation wall construction.

In an embodiment of the invention, the concrete compositions accordingto the invention are formed, set and/or hardened in the form of aconcrete masonry unit. As used herein, the term “concrete masonry unit”refers to a hollow or solid concrete article including, but not limitedto scored, split face, ribbed, fluted, ground face, slumped and pavingstone varieties. Embodiments of the invention provide walls thatinclude, at least in part, concrete masonry units made according to theinvention.

In an embodiment of the invention, the molded construction articles andmaterials and concrete masonry units described above are capable ofreceiving and holding penetrating fasteners, non-limiting examples ofsuch include nails, screws, staples and the like. This can be beneficialin that surface coverings can be attached directly to the moldedconstruction articles and materials and concrete masonry units moldedconstruction articles and materials and concrete masonry units.

In an embodiment of the invention, a standard 2½ inch drywall screw canbe screwed into a poured and set surface containing the present lightweight concrete composition, to a depth of 1½ inches, and is not removedwhen a force of at least 500, in some cases at least 600 and in othercases at least 700 and up to 800 pounds of force is appliedperpendicular to the surface screwed into for one, in some cases fiveand in other cases ten minutes.

The present invention is also directed to buildings that include the LWCcompositions according to the invention.

The present invention also provides a method of making an optimizedlightweight concrete article that includes:

-   -   identifying the desired density and strength properties of a set        lightweight concrete composition;    -   determining the type, size and density of polymer beads to be        expanded for use in the light weight concrete composition;    -   determining the size and density the polymer beads are to be        expanded to;    -   expanding the polymer beads to form expanded polymer beads;    -   dispersing the expanded polymer beads in a cementitious mixture        to form the light weight concrete composition; and    -   allowing the light weight concrete composition to set in a        desired form.

The desired density and strength properties of the set and/or hardenedLWC composition are determined based on the intended application.

In an embodiment of the invention, the type, size and density of polymerbeads to be expanded and the size and density the polymer beads are tobe expanded to can be determined based on empirical and/or publisheddata.

In another embodiment of the invention finite element analysis can beused to determine the type, size and density of polymer beads to beexpanded and the size and density the polymer beads are to be expandedto.

The resulting lightweight concrete composition is allowed to set and/orharden to provide LWC articles and concrete masonry units as describedabove.

The present invention will further be described by reference to thefollowing examples. The following examples are merely illustrative ofthe invention and are not intended to be limiting. Unless otherwiseindicated, all percentages are by weight and Portland cement is usedunless otherwise specified.

EXAMPLES

Unless otherwise indicated, the following materials were utilized:

-   -   Type III Portland Cement    -   Mason Sand (165 pcf bulk density, 2.64 specific gravity,        fineness modulus=1.74)    -   Potable Water—ambient temperature (˜70° F./21° C.)    -   Expandable Polystyrene—M97BC, F271C, F271M, F271T (NOVA        Chemicals Inc., Pittsburgh, Pa.)    -   EPS Resin—1037C(NOVA Chemicals, Inc.)    -   ½ inch Expanded Slate (Carolina Stalite Company, Salisbury,        N.C.—89.5 pcf bulk density/1.43 specific gravity)

Unless otherwise indicated, all compositions were prepared underlaboratory conditions using a model 42N-5 blender (Charles Ross & SonCompany, Hauppauge, N.Y.) having a 7-ft³ working capacity body with asingle shaft paddle. The mixer was operated at 34 rpm. Conditioning wasperformed in a LH-10 Temperture and Humidity Chamber (manufactured byAssociated Environmental Systems, Ayer, Mass.). Samples were molded in6″×12″ single use plastic cylinder molds with flat caps and were testedin triplicate. Compression testing was performed on a Formey FX250/300Compression Tester (Formey Incorporated, Hermitage, Pa.), whichhydraulically applies a vertical load at a desired rate. All otherperipheral materials (slump cone, tamping rods, etc.) adhered to theapplicable ASTM test method. The following ASTM test methods andprocedures were followed:

-   -   ASTM C470—Standard Specification for Molds for Forming Concrete        Test Cylinders Vertically    -   ASTM C192—Standard Practice for Making and Curing Concrete Test        Specimens in the Laboratory    -   ASTM C330—Standard Specification for Lightweight Aggregates for        Structural Concrete    -   ASTM C511—Standard Specification for Mixing Rooms, Moist        Cabinets, Moist Rooms, and Water Storage Tanks Used in the        Testing of Hydraulic Cements and Concretes    -   ASTM C143—Standard Test Method for Slump of Hydraulic-Cement        Concrete    -   ASTM C1231—Standard Practice for Use of Unbonded Caps in        Determination of Compressive Strength of Hardened Concrete        Cylinders    -   ASTM C39—Standard Test Method for Compressive Strength of        Cylindrical Concrete Specimens Cylinders were kept capped and at        ambient laboratory conditions for 24 hours. All cylinders were        then aged for an additional 6 days at 23±2° C., 95% relative        humidity. The test specimens were then tested.

Example 1

Polystyrene in unexpanded bead form (M97BC—0.65 mm, F271T—0.4 mm, andF271 M—0.33 mm) was pre-expanded into EPS foam (prepuff) particles ofvarying densities as shown in the table below.

Prepuff Particle Bead Bulk Bead Mean Size, Density, Standard deviation,Type μm lb/ft³ Mean Size, μm μm F271M 330 2.32 902 144 F271M 330 3.10824 80 F271M 330 4.19 725 103 F271T 400 2.40 1027 176 F271T 400 3.691054 137 F271T 400 4.57 851 141 M97BC 650 2.54 1705 704 M97BC 650 3.291474 587 M97BC 650 5.27 1487 584

The data show that the prepuff particle size varies inversely with theexpanded density of the material.

Example 2

Polystyrene in unexpanded bead form (0.65 mm, 0.4 mm, and 0.33 mm) waspre-expanded into prepuff particles with a bulk density of 2 lb/ft³ asshown in the table below. The prepuff particles were formulated into aLWC composition, in a 3.5 cubic foot drum mixer, that included 46.5 wt.% (25.3 vol. %) Portland cement, 16.3 wt. % (26.3 vol. %) water, and 1.2wt. % (26.4 vol. %) prepuff particles. The resulting LWC compositionshad a concrete density of 90 lb/ft². The average compressive strength(determined according to ASTM C39, seven day break test) is shown in thetable below.

Prepuff Particle Concrete Bead Bulk Density, Density, Compressive MeanSize, μm lb/ft³ lb/ft³ Strength, psi 650 2.00 90 1405 400 2.00 90 1812330 2.00 90 1521

The data show that as the mean unexpanded bead size decreases, at aconstant prepuff particle density, that surprisingly higher compressivestrength does not necessarily result from ever decreasing unexpandedbead size as suggested in the prior art. More particularly, the datashow that an optimum unexpanded bead size with respect to compressivestrength at 2.00 pcf exists when loaded to obtain 90 pcf concretedensity. This optimum appears to be between 330 microns and 650 micronsfor this particular formulation.

Example 3

Since the prepuff particle density also impacts the overall concretedensity, changing the EPS density requires a change in the EPS loadinglevel to maintain a constant concrete density. This relationship holdsonly as long as the total amount of prepuff particles is not so large asto compromise the strength of the surrounding concrete matrix. Therelationship between the prepuff particle density and loading levelprovides additional opportunities to optimize concrete strength whilecontrolling the overall concrete density.

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded intoprepuff particles having varying densities as shown in the table below.The prepuff particles were formulated into LWC compositions containingthe components shown in the table below, in a 3.5 cubic foot drum mixer,and each having a concrete density of 90 lb/ft³.

Sample A Sample B Sample C Prepuff Particle Bulk Density 1.26 3.29 5.37(lb/ft³) Portland Cement, wt. % 46.7 (28.5) 46.2 (22.1) 45.8 (18.9)(vol. %) Water, wt. % (vol. %) 16.4 (29.8) 16.2 (23) 16.1 (19.7) EPS,wt. % (vol. %) 0.7 (16.8) 1.8 (35.6) 2.6 (44.9) Sand, wt. % (vol. %)36.2 (24.9) 35.8 (19.3) 35.5 (16.5)

The following data table numerically depicts the relationship betweenprepuff density and concrete strength at a constant concrete density of90 lb/ft³.

Concrete Bead Prepuff Particle Density, Compressive Mean Size, μm BulkDensity, lb/ft³ lb/ft³ Strength, psi Sample A 650 1.26 90 1463 Sample B650 3.29 90 1497 Sample C 650 5.37 90 2157

The data show that as the prepuff particle density increases, thecompressive strength of the LWC composition also increases at constantconcrete density.

Example 4

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded intoprepuff particles having a bulk density of 1.11b/ft³ as shown in thetable below. The prepuff particles were formulated into LWCcompositions, in a 3.5 cubic foot drum mixer, containing the componentsshown in the table below.

Sample D Sample E Sample F Prepuff Particle Bulk Density 1.1 1.1 1.1(lb/ft³) Portland Cement, wt. % 46.8 (21.6) 46.3 (18.9) 46.1 (16.6)(vol. %) Water, wt. % (vol. %) 16.4 (22.5) 17 (20.6) 17 (18.2) EPS, wt.% (vol. %) 0.6 (37) 0.9 (44) 1.1 (50.8) Sand, wt. % (vol. %) 36.2 (18.9)35.9 (16.5) 35.8 (14.5)

The following data table numerically depicts the relationship betweenprepuff loading, concrete strength and concrete density.

Concrete Bead Prepuff Particle Density, Compressive Mean Size, μm BulkDensity, lb/ft³ lb/ft³ Strength, psi Sample D 650 1.1 89.6 1252 Sample E650 1.1 80.9 982 Sample F 650 1.1 72.4 817

The data show that as prepuff particle loading in the LWC compositionincreases at constant foam particle density, the light weight concretedensity and compressive strength decreases.

Example 5

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded intoprepuff particles having various densities as shown in the table below.The prepuff particles were formulated into LWC compositions, in a 3.5cubic foot drum mixer, containing the components shown in the tablebelow.

Sample G Sample H Sample I Sample J Prepuff Particle 1.1 2.3 3.1 4.2Bulk Density (lb/ft³) Portland Cement, 46.8 (21.6) 46.8 (26.8) 46.8(28.4) 46.8 (29.7) wt. % (vol. %) Water, wt. % 16.4 (22.5) 16.4 (28)16.4 (29.6) 16.4 (31) (vol. %) EPS, wt. % 0.6 (37) 0.6 (21.8) 0.6 (17.2)0.6 (13.4) (vol. %) Sand, wt. % 36.2 (18.9) 36.2 (23.4) 36.2 (24.8) 36.2(25.9) (vol. %)

The following table numerically depicts the relationship between prepuffdensity and concrete strength at a constant concrete prepuff loadingbased on the weight of the formulation.

Concrete Bead Prepuff Particle Density, Compressive Mean Size, μm BulkDensity, lb/ft³ lb/ft³ Strength, psi Sample G 650 1.1 89.6 1252 Sample H650 2.32 109.6 1565 Sample I 650 3.1 111.7 2965 Sample J 650 4.2 116.33045

The data show that as prepuff particle density in the light weightconcrete composition increases at constant prepuff particle loading (byweight), light weight concrete density and compressive strengthincreases.

Example 6

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded intoprepuff particles having various densities as shown in the table below.The prepuff particles were formulated into LWC compositions, in a 3.5cubic foot drum mixer, containing the components shown in the tablebelow.

Sample L Sample M Prepuff Particle Bulk Density 1.1 3.1 (lb/ft³)Portland Cement, wt. % (vol. %) 46.3 (18.9) 46.2 (21.4) Water, wt. %(vol. %) 17 (20.6) 16.2 (22.3) EPS, wt. % (vol. %) 0.9 (44) 1.8 (37.5)Sand, wt. % (vol. %) 35.9 (16.5) 35.8 (18.7)

The following table numerically depicts the relationship between prepuffdensity and concrete strength at a constant concrete density.

Concrete Bead Prepuff Particle Density, Compressive Mean Size, μm BulkDensity, lb/ft³ lb/ft³ Strength, psi Sample L 650 1.1 80.9 982 Sample M650 3.1 79.8 1401

The data show that as prepuff particle density in the LWC compositionincreases at constant concrete density, the compressive strength of theLWC increases.

Example 7

Polystyrene in unexpanded bead form (0.65 mm) was pre-expanded intoprepuff particles having various densities as shown in the table below.The prepuff particles were formulated into LWC compositions, in a 3.5cubic foot drum mixer, containing the components shown in the tablebelow.

Sample N Sample O Prepuff Particle Bulk Density 3.9 5.2 (lb/ft³)Portland Cement, wt. % (vol. %) 46 (21.5) 45.6 (21.4) Water, wt. % (vol.%) 16.1 (22.4) 16 (22.3) EPS, wt. % (vol. %) 2.3 (37.3) 3 (37.5) Sand,wt. % (vol. %) 35.6 (18.8) 35.4 (18.7)

The following data table numerically depicts the relationship betweenprepuff density and concrete strength at a constant concrete density.

Bead Prepuff Particle Concrete Mean Size, Bulk Density, Compressive μmlb/ft³ Density, lb/ft³ Strength, psi Sample N 650 3.9 85.3 1448 Sample O650 5.2 84.3 1634

The data show that as prepuff particle density in the LWC compositionincreases at constant concrete density, the compressive strength of theLWC increases.

Example 8

The following examples demonstrate the use of expanded slate as anaggregate in combination with the prepuff particles of the presentinvention. Polystyrene in unexpanded bead form was pre-expanded intoprepuff particles having various densities as shown in the table below.The prepuff particles were formulated into LWC compositions, in a 3.5cubic foot drum mixer, containing the components shown in the tablebelow.

Mixed expanded slate/EPS runs Example P Example Q Bead Mean Size, 0.330.4 micron Prepuff Particle Bulk 5.24 4.5 Density, pcf Weight % Cement19.84% 21.02% EPS 1.80% 1.44% Expanded slate 42.02% 39.07% Water 6.96%7.36% Volume % Cement 9.53% 10.34% EPS 22.71% 21.74% Expanded slate41.91% 39.91% Water 9.95% 10.78% LWC density (pcf) 90.9 93.7 LWCstrength (psi) 1360.0 1800.0

The data show that desirable light weight concrete can be obtained usingthe prepuff of the present invention and expanded slate as aggregate inlight weight concrete compositions.

Example 9

The following examples demonstrate the use of expanded slate as anaggregate used in combination with the prepuff particles of the presentinvention. Polystyrene in unexpanded bead form was pre-expanded intoprepuff particles having various densities as shown in the table below.The prepuff particles were formulated into LWC compositions, in a 3.5cubic foot drum mixer, containing the components shown in the tablebelow.

Example R Example S Example T Example U Example V Example W Bead size(mm) 0.5 0.4 0.4 0.4 0.4 0.4 Prepuff density (lb./ft³) 40 3.4 3.4 3.43.4 3.4 (unexpanded) Weight % Cement 34.4% 35.0% 36.2% 37.3% 35.9% 37.1%Sand 0.0% 23.2% 9.9% 0.0% 15.8% 1.9% EPS 25.0% 1.5% 1.4% 0.6% 1.5% 1.3%Slate 25.9% 26.3% 38.1% 47.1% 32.4% 44.7% Water 14.6% 14.0% 14.5% 14.9%14.4% 14.9% Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% water/cement0.43 0.40 0.40 0.40 0.40 0.40 Volume % Cement 15.8% 16.1% 16.1% 18.3%16.1% 16.1% Sand 0.0% 12.1% 5.0% 0.0% 8.0% 1.0% EPS 39.5% 27.3% 24.4%11.9% 26.4% 23.4% Slate 24.7% 25.2% 35.3% 48.0% 30.3% 40.3% Water 20.0%19.2% 19.2% 21.8% 19.2% 19.2% total 100.0% 100.0% 100.0% 100.0% 100.0%100.0% compressive strength 3813 2536 2718 4246 2549 2516 (psi) density(pcf) 89.3 91.1 90.7 98.0 89.7 89.9

Example 10

One-foot square, 4 inch thick concrete forms were made by pouringformulations prepared according to examples X and Y in the table belowinto forms and allowing the formulations to set for 24 hours.

Example X Example Y bead size (mm) 0.4 0.65 Prepuff density (lb/ft³) 3.44.9 wt % Cement 35.0% 33.1% Sand 23.2% 45.4% EPS 1.5% 2.9% Slate 26.3%0.0% Water 14.0% 13.2 total 100.0% water/cement 0.40 40.0% Volume %Cement 16.1% 16.0% Sand 12.1% 24.7% EPS 27.3% 40.3% Slate 25.2% 0.0%Water 19.2% 19.1% total 100.0% compressive strength 2536 2109 (psi)density (pcf) 91.1 90.6

After 7 days, a one-foot square, ½ inch sheet of plywood was fasteneddirectly to the formed concrete. A minimum of one-inch penetration wasrequired for adequate fastening. The results are shown in the tablebelow.

Fastener Example X Example Y 7 d coated nails attachment No penetrationwhen 100% penetration and slate is encountered attachment removal Easilyremoved Could not be manually removed from the concrete withoutmechanical assistance 2½ inch standard dry wall screw attachment Nopenetration when 100% penetration and slate is encountered attachment.Screw broke before concrete failed. removal Easily removed Could not bemanually removed from the concrete without mechanical assistance. Screwcould be removed and reinserted with no change in holding power.

The data demonstrates that the present light-weight concretecomposition, without slate, provides superior gripping capability withplywood using standard fasteners compared to traditional expanded slateformulations, while slate containing concrete did not readily acceptfasteners. This represents an improvement over the prior art as the timeconsuming practice of fixing anchors into the concrete to enable thefasteners to grip thereto can be eliminated.

Example 11

One-foot square, 4 inch thick concrete forms were made by pouring theformulations of Examples X and Y into forms and allowing theformulations to set for 24 hours. After 7 days, a one-foot square, ½inch sheet of standard drywall sheet was fastened directly to the formedconcrete using standard 1¾ inch drywall screws. A minimum of one-inchscrew penetration was required for adequate fastening. The results areshown in the table below.

Fastener Example X Example Y 1¾ inch standard dry wall screw attachmentNo penetration when slate 100% penetration and encountered isattachment. Screw could penetrate through the drywall. removal Easilyremoved. Could not be manually removed from the concrete withoutmechanical assistance. Screw could be removed and reinserted with nochange in holding power.

The data demonstrates that the present light-weight concretecomposition, without slate, provides superior gripping capabilitycompared to traditional expanded slate formulations, which did notreadily accept fasteners. This represents an improvement over the priorart as the time consuming practice of fastening nailing studs to theconcrete to allow for attaching the drywall thereto can be eliminated.

Example 12

Two-foot square, 4 inch thick concrete forms were made by pouring theformulations Examples X and Y into a form and allowing the formulationsto set for 24 hours. After 7 days, a three foot long, 2″×4″ stud wasfastened directly to the formed concrete using standard 16d nails. Aminimum of two-inch nail penetration was required for adequatefastening. The results are shown in the table below.

Fastener Example X Example Y 16 d nail attachment No penetration whenslate 100% penetration and is encountered attachment. removal Easilyremoved. Could not be manually removed from the concrete withoutmechanical assistance.

The data demonstrates that the present light-weight concretecomposition, without slate, provides superior gripping capabilitycompared to traditional expanded slate formulations, which did notreadily accept fasteners. This represents an improvement over the priorart as the expensive and time consuming practice of using TAPCON®(available from Illinois Tool Works Inc., Glenview, Illinois) or similarfasteners, lead anchors, or other methods known in the art to fastenstuds to concrete can be eliminated.

Example 13

Concrete without additional aggregate was made using the ingredientsshown in the table below.

Ex. AA Ex. BB Ex. CC Ex. DD Ex. EE Ex. FF Ex. GG Ex. HH Ex. II StartingBead F271T F271C M97BC F271T F271C M97BC F271T F271C M97BC bead size(mm) 0.4 0.51 0.65 0.4 0.51 0.65 0.4 0.51 0.65 Density (pcf) 1.2 1.3 1.53.4 3.3 3.4 5.7 5.5 4.9 Prepuff size (mm) 1.35 1.56 2.08 0.87 1.26 1.540.75 1.06 1.41 Expansion Factor 48 48 48 18 18 18 12 12 12 wt % Cement33.0 35.8 35.0 33.0 33.0 35.0 33.0 33.0 33.1 Sand 51.5 47.2 50.1 50.350.4 48.9 49.0 49.2 45.3 EPS 0.6 0.8 0.9 1.8 1.7 2.2 3.0 3.0 2.9 Water14.9 16.1 14.0 14.8 14.8 14.0 14.9 14.8 13.2 Volume % Cement 16.0 16.016.0 16.0 16.0 16.0 16.0 16.0 16.0 Sand 28.1 23.7 25.8 27.5 27.5 25.226.8 26.9 24.7 EPS 34.5 38.8 39.1 35.1 35.1 39.8 35.8 35.7 40.2 Water21.4 21.4 19.1 21.4 21.4 19.1 21.4 21.4 19.1 compressive 1750 1650 17201770 2200 1740 1850 2400 2100 strength (psi) density (pcf) 93 87 89 9092 88 89 90 90

The data shows that the average prepuff size required to provide maximumcompressive strength compositions is dependant, to some degree, on theexpansion factor of the prepuff. Focusing on average prepuff size alonedoes not provide a good indicator of maximum potential concretestrength. This point is illustrated by comparing examples BB and FF.Example FF (1.54 mm size) does not provide maximum compressive strengthat an 18× expansion factor, yet it is near the maximum strength that canbe obtained from beads expanded 48×.

Using a combination of prepuff size and expansion factor can provide anindicator for maximum concrete strength. As an example, example AA(prepuff size, 1.35 mm and expansion factor 48) provides 93 pcf concretewith a compressive strength of 1750 psi while a similarly sized prepuff,example 11 (prepuff size 1.41 mm and expansion factor 12) provides 90pcf concrete with a significantly higher compressive strength of 2100psi. Thus smaller prepuff size and a lower expansion factor can providehigher compressive strength in the present light weight concretecomposition within an optimum range of prepuff particle size.

Example 14

Concrete with expanded slate as an aggregate was made using theingredients shown in the table below.

Ex. JJ Ex. KK Ex. LL Ex. MM Ex. NN Ex. OO Ex. PP Ex. QQ Ex. RR StartingBead F271T F271T F271T F271T F271T F271T F271T F271T F271T bead size(mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Density (pcf) 3.4 3.4 3.4 3.43.4 3.4 3.4 3.4 3.4 Prepuff size (mm) 0.87 0.87 0.87 0.87 0.87 0.87 0.870.87 0.87 Expansion Factor 18 18 18 18 18 18 18 18 18 wt % Cement 35.933.0 30.5 35.9 33.0 30.6 35.9 33.0 30.6 Sand 0 8.2 15.6 10.6 18.0 24.321.1 27.7 33.2 EPS 1.1 0.8 0.5 1.3 1.0 0.7 1.6 1.2 0.9 Exp. Slate 48.744.8 41.3 37.8 34.8 32.2 27.0 24.9 23.0 Water 14.4 13.2 12.2 14.4 13.212.2 14.4 13.2 12.2 Volume % Cement 16.0 16.0 16.0 16.0 16.0 16.0 16.016.0 16.0 Sand 0 4.5 9.3 5.3 9.8 14.3 10.6 15.1 19.6 EPS 19.9 15.5 10.724.6 20.2 15.7 29.3 24.9 20.4 Exp. Slate 45.0 45.0 45.0 35.0 35.0 35.025.0 25.0 25.0 Water 19.1 19.1 19.1 19.1 19.1 19.1 19.1 19.1 19.1 7-day3220 3850 4070 2440 2890 3745 2300 2625 3695 strength (psi) Density(pcf) 92.8 98.5 102.7 90.7 96.8 101.5 88.1 94.5 101.3

The data indicates that while the EPS volume required to maintainapproximately 90 pcf density concrete decreases somewhat linearly as theslate concentration increases; the present light weight concrete'sstrength increases exponentially as the amount of slate in theformulation increases. This relationship highlights the potentiallysignificant impact of including aggregates in the present light weightconcrete formulation and demonstrates the potential for optimizing theamount of EPS and aggregates in the formulation to maximize strength ata desired density. In addition, the cost of various components can alsobe included in such a design and the light weight concrete formulationcan be optimized for both maximum strength and lowest cost.

Example 15

Concrete with unexpanded EPS (1037C) and no additional aggregate wasmade using the ingredients shown in the table below.

Ex. JJ Ex. KK Ex. LL bead size (mm) 0.51 0.51 0.51 Density (pcf) 40 4040 Expansion 1 1 1 Factor wt % Cement 38.7 33.0 28.8 Sand 0 21.6 37.8EPS 43.9 30.4 20.4 Water 17.4 14.9 13.0 Volume % Cement 16.0 16.0 16.0Sand 0 11.8 23.6 EPS 62.6 50.7 38.9 Slate 21.4 21.4 21.4 Water 16.0 16.016.0 compressive 2558 2860 3100 strength (psi) density (pcf) 76 89 100

The data show that unexpanded polystyrene resin beads (˜40 pcf bulkdensity) can provide a light weight concrete composition havingsurprisingly high compressive strength (2500-3200 psi) at low density(76-100 pcf).

Example 16

Prepuff from F271T bead expanded to 1.2 lb/ft³, F271C bead expanded to1.3 lb/ft³ and M97BC bead expanded to 1.5 lb/ft³ were evaluated usingscanning electron microscopy (SEM). The surface and inner cells of eachare shown in FIGS. 1 and 2 (F271T), 3 and 4 (F271C), and 5 and 6 (M97BC)respectively.

As shown in FIGS. 1, 3 and 5, the external structure of the prepuffparticles was generally sphereical in shape having a continuous surfaceouter surface or skin. As shown in FIGS. 2, 4 and 6, the internalcellular structure of the prepuff samples resembles a honeycomb-typesturcture.

The size of the prepuff particles was also measured using SEM, theresults are shown in the table below.

T prepuff (microns) (1.2 pcf) C prepuff (1.3 pcf) BC prepuff (1.5 pcf)Outer diameter 1216 1360 1797 Internal cell size 42.7 52.1 55.9 Internalcell wall 0.42 0.34 0.24 Cell wall/cell size 0.0098 0.0065 0.0043 Cprepuff (3.4 pcf) BC prepuff (3.1 pcf) Outer diameter — 1133 1294Internal cell size — 38.2 31.3 Internal cell wall — 0.26 0.47 Cellwall/cell size — 0.0068 0.0150

Taken with all of the data presented above, the data provide anindication that internal cellular structure might affect the strength ofa light weight concrete formulation.

When used in light weight concrete compositions, the prepuff particlescan impact the overall strength of the concrete in two ways. First, thelarger particles, which have a lower density, change the concrete matrixsurrounding the prepuff particle and secondly, the lower density prepuffparticle is less rigid due to the cell structure of the foamed particle.Since the strength of the concrete depends, at least to some extent, onthe strength of the prepuff particles, increased prepuff particlestrength should result in greater light weight concrete strength. Thepotential strength increase can be limited by the extent to which itimpacts the concrete matrix. The data in the present examples suggestthat the original bead particle size can be optimized to provide anoptimally sized prepuff particle (which is controlled by the prepuffdensity), which results in the highest possible lightweight concretestrength.

In other words, within an optimum prepuff particle size and optimumdensity range, the wall thickness of the prepuff will provide sufficientsupport to allow the present light weight concrete composition to havebetter strength than light weight concrete compositions in the priorart.

The data presented herein demonstrate that unlike the presumption andapproach taken in the prior art, expanded EPS particles can dosurprisingly more than act simply as a void space in the concrete. Morespecifically, the structure and character of the prepuff particles usedin the present invention can significantly enhance the strength of theresulting light weight concrete composition.

Example 17

This example demonstrates the use of fasteners with the present lightweight concrete composition and related pull-out strength. Thisevaluation was used to compare the load capacity of a screw directlyinstalled in the present light weight concrete (approximately 90 pcf)with conventional concrete fasteners installed in normal weight andtraditional lightweight concrete.

Fastener pullout testing was performed on three types of concrete:normal weight, 143 pcf (sample MM, 140 pcf normal concrete), lightweightconcrete using expanded slate (123 pcf) (sample NN, 120 pcf LWC), andlightweight concrete with EPS (87 pcf) (sample OO, 90 pcf LWC) made asdescribed above according to the formulations in the following table.

Sample MM Sample NN Sample OO 140 pcf 120 pcf 90 pcf EPS bead size (mm)— — 0.51 density (pcf) — — 3.37 wt % cement 20.2 24.8 32.9 sand 34.636.4 52.7 EPS — — 1.86 ⅜″ pea gravel 37.6 — — ½″ expanded slate — 29.4 —Water 7.7 9.41 12.51 vol % cement 16.0 16 16 sand 30.9 26.5 28.9 EPS — —37 ⅜″ pea gravel 35.0 — — ½″ expanded slate — 39.4 — Water 18.1 18.118.12 compressive 4941 9107 2137 strength (psi) density (pcf) 143 123 87

An apparatus was built that allowed weights to be hung vertically fromeach fastener using gravity to apply a load in line with the axis of thefastener. The 90 pcf LWC had 2½″ standard drywall screws directlyinstalled to approximately 1½″ depth. The 120 pcf LWC had two types offasteners installed into predrilled holes:2¾ TAPCON® metal screw-typemasonry fastening anchors (Illinois Tool Works Inc., Glenview, Ill.)installed approximately 2″ deep and standard 2¼″ expanding wedge-clipbolt/nut anchors installed approximately 1¼″ deep. The 140 pcf normalconcrete also had two types of fasteners installed into predrilledholes: 2¾″ TAPCON anchors installed approximately 2″ deep and standard2¼″ expanding wedge-clip bolt/nut anchors installed approximately 1¼″deep. One of the drywall screws in the light weight concrete was backedout and re-installed into the same fastener hole for testing. Also oneof the TAPCON screws was removed and reinstalled to evaluate any loss incapacity. The following tables show the data and loadings for eachanchor/fastener tested.

90 pcf LWC Drywall Screw Screw Extract and Stone 1: Length (in) Exposed(in) re-install (in) Strength (lb) Screw B 2.5 0.594 1.906 700 @ 30 sec.90 pcf LWC Drywall Screw Screw Stone 2: Length (in) Exposed (in)Installed (in) Strength (lb) Screw C 2.5 1.031 1.469 >740 > 10 min. 120pcf LWC TAPCON Screws Screw Extract and Stone 3: Length (in) Exposed(in) re-install (in) Strength (lb) Screw C 2.75 0.875 1.875 >740 > 10min. 120 pcf LWC Bolt/Sleeve/Nut Anchor Stone 4: Length (in) Exposed(in) Installed (in) Strength (lb) Anchor D 2.25 0.875 1.375 >740 > 10min. 140 pcf normal concrete TAPCON Screws Screw Extract and Stone 5:Length (in) Exposed (in) re-install (in) Strength (lb) Screw C 2.750.906 1.844 >740 > 10 min. 140 pcf normal concrete Bolt/Sleeve/NutAnchor Stone 6: Length (in) Exposed (in) Installed (in) Strength (lb)Anchor C 2.25 1.094 1.156 >740 > 10 min.

The holding power of the drywall screws in the 90 pcf LWC wassurprisingly high as they did not easily break or tear from theconcrete. The drywall screws were easy to install, only requiring astandard size electric drill. The gripping strength of the drywallscrews in the 90 pcf LWC was such that if the applied drilling torquewas not stopped before the screw head reached the surface of theconcrete, the head of the screw would twist off. All of the fastenersheld the 740 lbs. of load for at least 10 minutes except the backed outand re-inserted drywall screw in the 90 pcf LWC, which held 700 lbs. for30 seconds before tearing loose from the concrete. This drywall screwdid not break at the failure point, but pulled out of the concrete.

Taking the above data as a whole, it has been demonstrated that anoptimum prepuff bead size exists (as a non-limiting example,approximately 450-550 μm resin beads expanded to an expansion factor ofapproximately 10-20 cc/g to a prepuff diameter of approximately 750 to1400 μm for 90 pcf lightweight concrete) to maximize the compressivestrength of the present light weight concrete formulations. Thecompressive strength of the present light weight concrete formulationscan be increased by increasing the present EPS prepuff bead density.Unexpanded polystyrene resin (˜40 pcf bulk density) yields LWC of highcompressive strength (2500-3200 psi) considering the low density (76-100pcf). Aggregates can be used in the present light weight concreteformulations. The present light weight concrete formulations, withoutcourse aggregates, provide a concrete composition, which may be directlyfastened to using standard drills and screws. When the EPS prepuff beadsare expanded to low bulk densities (for example <1 pcf), the beads havea weak internal cellular structure, which creates a weaker foam, and inturn provides a light weight concrete composition having a lowercompressive strength.

The present invention has been described with reference to specificdetails of particular embodiments thereof. It is not intended that suchdetails be regarded as limitations upon the scope of the inventionexcept insofar as and to the extent that they are included in theaccompanying claims.

We claim:
 1. A pre-cast and pre-stressed construction article containinga lightweight concrete composition comprising from 10 to 90 volumepercent of a cement composition, from 10 to 90 volume percent ofparticles having an average particle diameter of from 0.2 mm to 3 mm, abulk density of from 0.028 g/cc to 0.48 g/cc, an aspect ratio of from 1to 3, and have a continuous outer layer, from 0 to 50 volume percent ofaggregate, and less than one percent by weight with respect to totalweight of the composition of air-entraining agents; wherein the sum ofcomponents used does not exceed 100 volume percent; wherein the concretecomposition has a density of from about 90 to about 130 lb./ft³; andwherein after the lightweight concrete composition is set for sevendays, has a compressive strength of at least 1700 psi as testedaccording to ASTM C39.
 2. A lightweight concrete article made accordingto a method comprising: identifying the density and strength propertiesof a set lightweight concrete composition; determining the type, sizeand density of polymer beads to be expanded for use in the lightweightconcrete composition; determining the size and density the polymer beadsare to be expanded to; expanding the polymer beads to form expandedpolymer beads; dispersing the expanded polymer beads in a cementitiousmixture containing a hydraulic cement composition to form thelightweight concrete composition; and allowing the lightweight concretecomposition to set in a desired form; wherein the lightweight concretecomposition comprises from 10 to 90 volume percent of a cementcomposition, from 10 to 90 volume percent of particles having an averageparticle diameter of from 0.2 mm to 3 mm, a bulk density of from 0.028g/cc to 0.48 g/cc, an aspect ratio of from 1 to 3, and have a continuousouter layer, from 0 to 20 volume percent of coarse aggregate, from 10 to50 volume percent of fine aggregate, and less than one percent by weightwith respect to total weight of the composition of air-entrainingagents; wherein the sum of components used does not exceed 100 volumepercent; wherein the concrete composition has a density of from about 90to about 130 lb./ft³; and wherein after the lightweight concretecomposition is set for seven days, has a compressive strength of atleast 1700 psi as tested according to ASTM C39.
 3. A pre-castconstruction article containing a concrete composition comprising from10 to 90 volume percent of a cement composition, from 10 to 90 volumepercent of particles having an average particle diameter of from 0.2 mmto 3 mm, a bulk density of from 0.028 g/cc to 0.48 g/cc, an aspect ratioof from 1 to 3, and have a continuous outer layer, from 0 to 50 volumepercent of aggregate, and less than one percent by weight with respectto total weight of the composition of air-entraining agents; wherein thesum of components used does not exceed 100 volume percent; wherein theconcrete composition has a density of from about 90 to about 130lb./ft³; and wherein after the lightweight concrete composition is setfor seven days, has a compressive strength of at least 1700 psi astested according to ASTM C39.
 4. The construction article according toclaim 3, wherein the particles comprise expanded polymer particleshaving an inner cell wall thickness of at least at least 0.15 μm.
 5. Theconstruction article according to claim 3, wherein the particlescomprise expanded polymer particles comprising one or more polymersselected from the group consisting of homopolymers of vinyl aromaticmonomers; copolymers of at least one vinyl aromatic monomer with one ormore of divinylbenzene, conjugated dienes, alkyl methacrylates, alkylacrylates, acrylonitrile, and/or maleic anhydride; polyolefins;polycarbonates; polyesters; polyamides; natural rubbers; syntheticrubbers; and combinations thereof.
 6. The construction article accordingto claim 3, wherein the particles comprise expanded polymer particlesprepared by expanding a polymer bead having an unexpanded average resinparticle size of from about 0.2 mm to about 2 mm.
 7. The constructionarticle according to claim 3, wherein the cement composition comprisesone or more materials selected from the group consisting of Portlandcements, pozzolana cements, gypsum cements, aluminous cements, magnesiacements, silica cements, and slag cements.
 8. The construction articleaccording to claim 3, wherein the concrete composition comprises sand,fine aggregate, coarse aggregate, plasticizers and/or fibers.
 9. Theconstruction article according to claim 8, wherein the fibers areselected from the group consisting of glass fibers, silicon carbide,aramid fibers, polyester, carbon fibers, composite fibers, fiberglass,combinations thereof, fabric containing said fibers, and fabriccontaining combinations of said fibers.
 10. The construction articleaccording to claim 3, wherein a standard 2 ½ inch drywall screw, screwedinto the formed and set concrete composition to a depth of 1 ½ inches,is not removed by applying 500 pounds of force perpendicular to thesurface screwed into for one minute.
 11. The construction articleaccording to claim 2, wherein the particles comprise expanded polymerparticles prepared by expanding a polymer bead having an unexpandedaverage resin particle size of from about 0.2 mm to about 2 mm.
 12. Theconstruction article according to claim 11, wherein the particlescomprise polystyrene.
 13. The construction article according to claim 2,wherein the coarse aggregate is selected from the group consisting ofstone, gravel, ground granulated blast furnace slag, fly ash, glass,expanded slate, clay; pumice, perlite, vermiculite, scoria, diatomite,expanded shale, expanded clay, expanded slag, pelletized aggregate,extruded fly ash, tuft, macrolite, slate, expanded blast furnace slag,sintered fly ash, coal cinders, and combinations thereof.
 14. Theconstruction article according to claim 2, wherein the fine aggregatecomprises sand.
 15. The construction article according to claim 2,wherein the lightweight concrete composition comprises from 0.1 to 1volume percent of one or more additives selected from the groupconsisting of anti-foam agents, water-proofing agents, dispersingagents, set-accelerators, set-retarders, plasticizing agents,superplasticizing agents, freezing point decreasing agents,adhesiveness-improving agents, colorants and combinations thereof. 16.The construction article according to claim 1, wherein the particlescomprise expanded polymer particles prepared by expanding a polymer beadhaving an unexpanded average resin particle size of from about 0.2 mm toabout 2 mm.
 17. The construction article according to claim 1, whereinthe construction article comprises prestressing tendons.
 18. Theconstruction article according to claim 1, wherein the lightweightconcrete composition comprises from 0.1 to 1 volume percent of one ormore additives selected from the group consisting of anti-foam agents,water-proofing agents, dispersing agents, set-accelerators,set-retarders, plasticizing agents, superplasticizing agents, freezingpoint decreasing agents, adhesiveness-improving agents, colorants andcombinations thereof.
 19. The construction article according to claim 1,wherein the lightweight concrete composition is free of air entrainingagents.
 20. The concrete article according to claim 2, wherein thelightweight concrete composition is free of air entraining agents. 21.The construction article according to claim 3, wherein the lightweightconcrete composition is free of air entraining agents.
 22. A dry mixturecomprising: 10 to 90 volume percent of a cement composition, 10 to 90volume percent of expanded particles having an average particle diameterof from 0.2 mm to 3 mm, a bulk density of from 0.028 g/cc to 0.52 g/cc,an aspect ratio of from 1 to 3, and a continuous outer layer, 0 to 50volume percent of one or more aggregates, and 0 to 1 volume percent ofone or more additives; wherein the sum of components used does notexceed 100 volume percent; wherein the dry mixture is packaged forfuture use; wherein after the dry mixture is mixed with a sufficientamount of water to cause the mixture to set and bind, the resultingconcrete composition has a density of from 90 to about 130 lb./ft³ and aseven day compressive strength of at least 1700 psi as determinedaccording to ASTM C39.
 23. The mixture according to claim 22, whereinthe expanded particles comprise one or more polymers selected from thegroup consisting of homopolymers of vinyl aromatic monomers; copolymersof at least one vinyl aromatic monomer with one or more ofdivinylbenzene, conjugated dienes, alkyl methacrylates, alkyl acrylates,acrylonitrile, and/or maleic anhydride; polyolefins; polycarbonates;polyesters; polyamides; natural rubbers; synthetic rubbers; andcombinations thereof.
 24. The mixture according to claim 22, wherein theparticles comprise expanded polymer particles prepared by expanding apolymer bead having an unexpanded average resin particle size of fromabout 0.2 mm to about 2 mm.
 25. The mixture according to claim 22,wherein the cement composition comprises a hydraulic cement composition.26. The mixture according to claim 25, wherein the hydraulic cementcomprises one or more materials selected from the group consisting ofPortland cements, pozzolana cements, gypsum cements, gypsumcompositions, aluminous cements, magnesia cements, silica cements, andslag cements.
 27. The mixture according to claim 22, wherein thecementitious mixture comprises fine aggregate, coarse aggregate,plasticizers and/or fibers.
 28. The mixture according to claim 27,wherein the fibers are selected from the group consisting of glassfibers, silicon carbide, aramid fibers, polyester, carbon fibers,composite fibers, fiberglass, combinations thereof, fabric containingsaid fibers, and fabric containing combinations of said fibers.
 29. Themixture according to claim 22 comprising one or more materials selectedfrom the group consisting of stone, gravel, ground granulated blastfurnace slag, fly ash, glass, silica, expanded slate, clay; pumice,perlite, vermiculite, scoria, diatomite, expanded shale, expanded clay,expanded slag, fumed silica, pelletized aggregate, extruded fly ash,tuft, macrolite, slate, expanded blast furnace slag, sintered fly ash,coal cinders, and combinations thereof.
 30. The mixture according toclaim 22, wherein the additives are selected from the group consistingof anti-foam agents, water-proofing agents, dispersing agents,set-accelerators, set-retarders, plasticizing agents, superplasticizingagents, freezing point decreasing agents, adhesiveness-improving agents,colorants and combinations thereof.
 31. The mixture according to claim22, wherein the expanded particles are expanded polystyrene particles.32. The mixture according to claim 31, wherein the cement composition ispresent at from 10 to 60 volume percent and comprises a Portland Cement;the expanded polystyrene particles are present at from 20 to 78 volumepercent, the aggregates are present at from 5 to 35 volume percent, andone or more additives are present at from 0.1 to 1 volume percent.
 33. Adry mixture for mixing later with water to form a concrete structurecomprising: 22 to 90 volume percent of cement; 10 to 90 volume percentof expanded particles having an average particle diameter of from 0.2 mmto 3 mm, a bulk density of from 0.028 g/cc to 0.52 g/cc, an aspect ratioof from 1 to 3, and a continuous outer layer, 0.5 to 5 volume percent offibers; 0 to 60 volume percent of one or more aggregates, 0 to 3 volumepercent by weight of an ethylene/vinyl acetate copolymer; 0 to 3 volumepercent of an anti-foam agent; 0 to 3 volume percent of a water reducer;and 0 to 3 volume percent of a plasticizer; wherein the sum ofcomponents used does not exceed 100 volume percent; wherein after thedry mixture is mixed with a sufficient amount of water to cause themixture to set and bind, the resulting concrete composition has adensity of from 90 to about 130 lb./ft³ and a seven day compressivestrength of at least 1700 psi as determined according to ASTM C39. 34.The mixture according to claim 33, wherein the cement compositioncomprises a hydraulic cement composition.
 35. The mixture according toclaim 33, wherein the hydraulic cement comprises one or more materialsselected from the group consisting of Portland cements, pozzolanacements, gypsum cements, gypsum compositions, aluminous cements,magnesia cements, silica cements, and slag cements.